I bought too much hay last season. Fine orchard grass, nicely cured, nice color and scent, no dust or mold, good stuff.
I have enough to feed next winter too.
I've read that hay can lose some of it's nutrients if stored for too long, but it's not enough to get tense about.
The hay is in a loft and it gets hotter-than-heck up there in the summer. Will the heat really hurt this hay? Or should I sell it now?
Definitely don't sell it! You have no idea what the availability of hay will be for next winter.
If you're concerned about the nutrients, you could do a hay analysis in the fall.
I was that fortunate two years ago but then I had a bumper crop of mice and when I went to start feeding the hay I found that it was all full of mouse nests and droppings. Fortunately I found that out before it was too late to find hay. I hope you have better luck!
Well, hay in the barn is like money in the bank, you never know what kind of natural disasters the next year will bring and what hay prices will be like or quality, so if you have nice stuff its wise to hold onto it.
OTOH, if you live in an area where hay is generally plentiful and disasters really don't have a huge impact, then I would probably hang on to enough to make it one month past the date of my preferred cutting and sell the rest. You might be able to sell it at a premium and partially pay for your 2013 hay, or you could really make someone's day who's struggling for hay right now.
I don't like the idea of hay cooking in a hot loft all year, but as far as I know it doesn't completely kill the nutritional aspect, though it does degrade on its own over time anyhow.
Long term storage hay can also sometimes become dusty from breaking down.
A judgement call like this is really a regional thing, climate, ease or hardship of getting hay each year, pricing, etc.
Ask yourself: "Can I do anything about this?"
If you can, do it. If you can't... then you can't and leave it at that. Worrying achieves nothing but stress.